This invention generally relates to remote signalling devices used, in vehicle security systems for example and, more particularly, to a system for controlling the strength of a signal transmitted by the remote signalling device.
A variety of remote signalling devices are commercially available. Examples include garage door opener systems, home security lighting systems, estate gate opening systems and vehicle security and alarm systems. In most cases, these systems include a portable, low power, radio frequency transmitter. Even though a wide variety of such devices are commercially available, those skilled in the art are always striving to make improvements and there is a need for enhanced and improved capability.
For example, a recent trend includes incorporating the ability to remotely communicate with a variety of devices from a single remote signalling transmitter. It is useful for a vehicle owner, for example, to be able to use a single transmitter to remotely operate a vehicle security system and a garage door opener using a single transmitter. Utilizing individual transmitters for multiple systems is cumbersome and inconvenient.
When one tries to incorporate different transmitter circuits into a single transmitter to accommodate the different signals for the different systems, several difficulties are encountered. One problem is associated with cost and "universal" application for a transmitter. When individual transmitter circuits are utilized, the cost typically increases for each signalling device. Moreover, even where individual transmitter circuits are utilized, fixed signal levels from the transmitter cannot be optimized for differing modulation duty cycles of the various transmissions that may need to be generated. An additional challenge that is presented is that the carrier frequency and modulation duty cycle of the ultimate signals to be transmitted are typically not known to the manufacturer, which can make it challenging to design circuitry that will accommodate all of the signals that a particular consumer desires.
Another problem that is typically faced with remote signalling devices is that the battery or power source supply voltage typically decreases during the normal lifetime of the signalling device. A decreasing supply voltage usually results in a reduced signal strength. Over time, therefore, most remote signalling devices become ineffective for communicating with the desired system controller.
Another consideration is complying with regulatory limits. Limitations on signal levels poses another challenge that must be overcome when trying to adjust signal strength to optimize performance.
This invention provides a solution to the difficulties faced in designing such a remote signalling device. Moreover, this invention has usefulness in all remote signalling devices where power management can enhance the performance of the signalling device.